The invention relates to a withdrawal system in accordance with the preamble of claim 1.
A withdrawal system of that type is known from EP 0 977 702 B1. This withdrawal system serves to fill and empty containers, especially barrels, that are filled with liquid chemicals. The withdrawal system described there has a container closure. The container closure is generally inserted into a container opening seating a bung head. The container closure itself has an immersion pipe, capable of being connected to the bung head, via which liquids stored in the container can be removed and via which liquids can be fed into the container. Furthermore, the container closure has an extraction connector element that is typically designed in the form of an extraction head and that can be connected to the bung head.
A fluid is then removed from the container via the extraction connector element or, if applicable, a fluid is also fed in. A pump is connected via the extraction connector element here to carry out the removal or supply of a fluid.
The liquids stored in the containers typically involve special liquid chemicals. Even based on safety reasons alone, liquids have to be capable of being withdrawn from the containers, just as the liquids have to be capable of being fed into the containers, without the possibility of a mistake. Furthermore, a withdrawal of this type that rules out a mix-up is also required for reasons relating to a minimization of contamination, because the connection of an incorrect extraction connector element that was already used for different chemicals would lead to contamination of the chemicals in the container that the extraction connector element is coupled with.
To prevent the risk of a mix-up of that type, a suggestion is made in EP 0 977 702 B1 to provide coding recesses in the bung head of the respective container. An annular disk with coding studs is assigned to the extraction connection element accompanying the container by attaching the annular disk in a coupling stopper that is screwed onto the extraction connector element to fix it in place on the bung head.
The coding studs of the annular disk form an unambiguous, individualized coding in such a way that the coding studs only fit the coding recesses of the matching container. A connection of the extraction connector element to the associated container that rules out a mix-up is therefore ensured.
A drawback here, however, is the fact that additional mechanical parts are required to rule out a mix-up with the coding studs and the coding recesses, which substantially increases the construction expense of the container closure. One drawback in particular is that the coding studs are arranged on an annular disk that has to be fit as a separate accessory part into the design of the container closure, which is why the container closure has an expensive design structure. A further drawback is that the mechanical coding can be manipulated by removing all of the studs on the extraction head.